When it comes to easing sanctions on Iran, the nuclear accord reached in Vienna is a work of diplomatic abstract art — a composition so complex it lets each side see what it wants.

As word spread Tuesday of the agreement, Iranian President Hassan Rouhani wrote on Twitter, with a dash of snark: “Upon #IranDeal implementation all sanctions will be lifted — not suspended. Otherwise, there was no need for 18-day round-the-clock #IranTalks.”

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President Barack Obama, meanwhile, stressed in a speech that sanctions “relief will be phased in,” and that “Iran must complete key nuclear steps before it begins to receive new sanctions relief.” The sanctions, he added, could quickly be reimposed.

The differences in emphasis and terminology (“lifted”? “suspended”? “relief”?) aren’t an accident given the way the deal is structured, but they also ensure that the unwinding of sanctions — including a U.N. arms embargo that covers conventional weapons — will remain a potential flashpoint in the months and years to come.

The 100-plus page accord lays out a multi-stage process when it comes to lifting sanctions. In one, Iran takes steps to dismantle its nuclear program while the U.S., United Nations and European Union lay the legal groundwork for lifting nuclear-related sanctions. Then on what’s being called “Implementation Day” (even though it’s unclear how it will all fit in a day) U.N. inspectors must verify Iran has taken the steps required of it, and the U.S., the U.N. and the EU will pass resolutions or take other steps to formally waive the sanctions.

This staged implementation allows the United States to say that the international community didn’t lift sanctions until after Iran had dismantled much of its nuclear infrastructure. At the same time, it allows Iranian leaders to refer to “Implementation Day” as the real day the agreement takes effect, casting the official waiving of sanctions as a victory for the Iranian people.

“This was the optimal middle point,” said Ilan Goldenberg, a former State Department official with expertise on the Middle East. “Any difficult international negotiation like this one has to meet both sides’ domestic political bottom lines. That is what this agreement does. It doesn’t work otherwise.”

The sanctions regime began to build in the wake of Iran’s 1979 revolution when the United States broke off diplomatic relations. The sanctions imposed over time dealt not just with nuclear concerns but also the country’s backing of terrorist organizations, its ballistic missile aims and its human rights abuses.

For decades the U.S. was mostly alone in sanctioning Tehran. But after inspectors determined in 2005 that Iran was not meeting its international nuclear obligations, the E.U. and the U.N. got on board the sanctions bandwagon. Over the next decade, the U.S., the E.U. and U.N. would impose layers of sanctions on Iran that included an arms embargo and penalties related to Iran’s oil industry; the U.N.’s involvement was a powerful signal to national governments to cooperate with the sanctions.

By 2013, Iran’s economy was cratering and inflation soared above 40 percent and its diplomats returned to the negotiating table. As the talks went on, both sides tried to rein in each other’s expectations, including warning the Iranians about the limits of U.S. democracy, sources familiar with the process said.

For instance, early on, Iranian officials thought there might be a chance that Congress could repeal the sanctions it had put in place against the Islamic Republic, said Richard Nephew, a former State Department official who previously served as lead sanctions expert for the U.S. team negotiating with Iran.

U.S. officials had to explain that even if the Obama administration wanted such a thing (it didn’t) there was no way the Republican-led Congress would go along. (Under the new agreement, President Barack Obama can waive the relevant congressional sanctions, but they’ll still remain in the statutes.)

Throughout the negotiations, Iranian officials would often bring up the same issues over and over, as if to see if they could get a different answer from the other side.

“There were multiple times during the process they’d claimed they’d never heard before what we were prepared to do, but then we sat down and briefed them on it for the umpteenth time,” said Nephew, who served on the negotiating team for a year and a half before leaving in December.

One sanctions-related issue the Iranians kept raising was the potential that after a deal was reached, the U.S. will reimpose or level new sanctions against Tehran for reasons other than its nuclear program. Already, the U.S. has said it will not lift sanctions put in place over its support for terrorist groups, human rights abuses or ballistic missile aims.

“We told them that we understand it’s a concern, (but) we could not accept a restraint on us to impose sanctions for other reasons because they would not accept restraints on their other actions,” Nephew recalled.

It’s unclear what sort of assurances the Obama administration has offered Iran on this front in more recent months, but there are references in the agreement to the various sides trying to avoid actions that undermine its spirit. But it’s also likely hawkish members of Congress will push for more non-nuclear-related sanctions in the coming months.

(One other potential complication, analysts note, is that even if a huge number of sanctions are lifted in a short time, it could be months, even years, before international companies feel comfortable investing in Iran, dragging out its economic struggles longer than many Iranians would like.)

Iranian negotiators also asked if there was a way to guarantee that suspended sanctions would stay suspended, even if a new president took office, Nephew said. The Americans would acknowledge the possibility that a new president could reimpose sanctions, but they’d point out that a future Iranian leader could also choose to restart the country’s nuclear program.

The point was that the deal had to be constructed in a way that made it painful for both sides to cheat or change direction. “All negotiations and contracts involve a mutual exchange of risks,” Nephew said. “In my opinion, that’s what we’re doing here.”

As the nuclear talks entered the final stretch, Iranian officials threw in another sanctions-related wrinkle: they demanded the U.N. lift an arms embargo that bars Iran from access to many conventional weapons, such as tanks and aircraft. Iran argued that because the U.N. imposed the arms embargo to stop its nuclear program, it should be fully lifted as part of the deal.

The U.S., however, does not want to see Iran get more weapons of any kind at a time of so much turmoil in the Middle East. Tehran already is responsible for much of that turmoil, either directly or through its use of militias in countries such as Syria, Lebanon and Iraq. Sunni Arab states, as well as Israel, are especially worried about the possibility of Iran purchasing more weapons, noting that under the sanctions relief it does get it will eventually be able to get access to more than $100 billion in frozen assets.

The accord — at least what’s been released publicly — is vague on the exact future of the arms embargo. Obama, however, said the ban on conventional weapons sales will last another five years. He also said restrictions on Iranian access to ballistic missile technology would continue for eight years. The restrictions are expected to be spelled out in a new U.N. Security Council resolution.

Throughout the process, Iranians have been aiming for a deal that has a high level of reciprocity so that when they present it back home they can show they got as much out of it, especially in sanctions relief, as the world powers that want to restrict Iran’s nuclear capabilities.

Rouhani, in a speech to Iranians on Tuesday, was clear about this, saying, “This is a mutual deal, a reciprocal deal,” according to news reports.

The desire for reciprocity also seemed to be one reason for some of the comments by Iran’s Supreme Leader Ayatollah Ali Khamenei, who has final say on all matters of state in Iran.

In one case, Khamenei declared just days after a preliminary deal was reached that sanctions “should be lifted all together on the same day of the agreement.” And in a tweet, Khamenei wrote, “All economic, financial & banking sanctions, either by UNSC, US Congress or administration must be lifted on same day deal is signed.”

Analysts, however, say the aging cleric’s comments, when examined closely, always left some wiggle room for his negotiators. The word “signed,” some experts said, offered an escape hatch because it could be interpreted to refer to the certification by U.N. inspectors on “Implementation Day.”

Reza Marashi, a top official with the National Iranian American Council, a group that supports the talks and has contacts with both the U.S. and Iranian negotiating teams, said Iran wanted to make sure sanctions relief was addressed with the same scope in the deal as the curbs on its nuclear program.

After all, both Obama and Rouhani have to please different audiences. In Iran, Rouhani has to wade through what could be stiff opposition among hardliners furious over curbs on a program they see as a matter of national pride.